Fig. 4.

Single-channel conductances of selectivity filter variants. (A) Example current–voltage relationships for individual PKA-phosphorylated CFTR variants reconstituted in synthetic planar lipid bilayers. Symmetric recording buffer contained 150 mM chloride. Three mM ATP was included in the upper recording chamber only. Membrane potentials are indicated using physiological convention. (B) Single-channel conductances of the wild-type CFTR and selectivity filter variants. Data represent means and SE for 4 to 42 channels and were fitted with quadratic functions of the form i = γ₀V + cV² to account for the subtle inward rectification. Conductances at 0 mV (γ₀) are reported.